1. Field of the Invention
The present invention relates to optical and millimeter-wave systems. More specifically, the present invention relates to devices used to reflect millimeter-wave frequencies and transmit optical frequencies.
2. Description of the Related Art
High-power millimeter-wave systems sometimes require the placement of lasers and/or cameras in the path of the millimeter-wave beam. In order to prevent damage to the equipment, a shield needs to be placed in the path of the beam. The shield needs to be almost totally reflective at millimeter-wave frequencies and transparent at optical frequencies.
In material processing applications, for instance, millimeter-waves may be used inside a reaction chamber to fabricate a synthetic substance. It may be necessary or desirable to place a window in the chamber in order to observe the reaction taking place within. This window needs to transmit optical frequencies without distorting them, while blocking transmission of the millimeter-waves.
Previous attempts to solve this problem have used either metal meshes or absorptive water-filled windows. Metal meshes are effective at reflecting nearly all of the incident radiation, but they are only marginally transparent at optical frequencies.
While the performance of absorptive water-filled windows is superior to that of metal meshes, they are subject to several problems. First, they may be prone to leaks after extended use. In addition, the perception exists among users than an incident millimeter-wave beam of sufficient intensity could cause the water to boil, which could lead to catastrophic failure of the window. Finally, it has been observed experimentally that when an absorptive water window is radiated by a high-power millimeter-wave beam, the absorbed power initiates convection currents in the water that scatters incident light, degrading the images captured by a camera behind the window.
Hence, a need exists in the art for a system or method for reflecting millimeter-wave frequencies and transmitting optical frequencies without distorting the optical frequencies.